Final answer:
If a pharmacist suspects a customer is trying to purchase pseudoephedrine or ephedrine for illegal purposes, they must deny the sale and might have to report their suspicion to law enforcement.
Step-by-step explanation:
If the pharmacist (or intern) determines that the customer is attempting to purchase pseudoephedrine/ephedrine for illegitimate purposes, the sale should be denied. Pseudoephedrine and ephedrine are regulated substances due to their potential for abuse and their role as precursors in the illicit manufacture of methamphetamine. Pharmacists have a legal and ethical obligation to ensure that these drugs are dispensed only for legitimate medical purposes. If a pharmacist suspects illegal activity, they should refuse the sale and may also be required to report their suspicions to law enforcement, depending on local regulations.